The invention relates to unsaturated polyester resins and more particularly polyester resin compositions curable at room temperature and comprising divinyl ethers, which compositions are specially suitable for gelcoats, lamination resins and applications where thicker layers of the product are required.
Various vinyl and divinyl ethers have been used as monomer replacing agents in different polyester formulations of the state of the art. A benefit which is achieved by using vinyl ethers, is the replacement of more harmful monomers with non-hazardous vinyl compounds, which are sufficiently reactive under appropriate curing conditions and which can be cured as part of the finished product. One of the major problems relating to the applicability of these resin compositions in normal unsaturated polyester resin concerns curing. In most of the examples presented in literature, the resins can be cured only by radiation. U.S. Pat. No. 5,360,863 describes the use of vinyl ethers as an alternative to acrylates and methacrylates in radiation curable unsaturated polyester compositions. This publication discloses the replacing of volatile monomers like styrene or low molecular weight methacrylates/acrylates by vinyl ethers but the compositions presented in the patent are only radiation curable. Similarly, EP patent 322 808 describes the use of divinyl ethers with ethylenically unsaturated polyesters in radiation curable compositions. An additional feature of the invention in this publication is to allow divinyl ether to react to iso-cyanates in order to obtain vinyl ether modified polyurethane intermediates. WO 90/01512 describes more generally the use of vinyl ethers in photo-curable compositions.
Curing by radiation sets great limitations for vinyl ether compounded polyesters in applications, such as construction, because the versatility of applications and the thickness of moulded layers are significantly limited. Moulds of larger size are difficult or impossible to expose to any radiation and even if the moulded parts could be cured by radiation, radiation does not penetrate the thick layers of reinforced materials. For the above mentioned reasons the typically used unsaturated polyester formulations containing vinyl ethers are suitable only for UV (ultra violet) or EB (electron beam) curable coatings.
EP application 0582909 discloses at room temperature radical curable compositions specially suitable for thin films and coatings of approx. 90 xcexcm thickness which compounds comprise unsaturated polyesters based on unsaturated dicarboxylic acids and unsaturated glycolic oxalkylated 2-buten-1,4-diols, and (meth)acrylates. Compounds with vinyl ether groups may also or alternatively used. By using the unsaturated glycolic components the density of unsaturation is raised thus increasing the total reactivity of the polyesters sufficient for thin coatings. Additionally the compositions comprise known additives. DE application 19711410 discloses compositions for impregnation, filling and coating of electrotechnical and electronic building parts and for impregnation or isolation materials. The composition which is suitable for impregnation and for coating with thin films, comprises a polyester component A1) which contains as building blocks dihydrodicyclopentadienyl units and/or oligo-dihydrodicyclopentadienyl units, a vinyl ether component (A2) and an additional polymer component (A3) and other additives. These dicyclopentadienyl based polyester resins are cured by methods requiring photo-initiation or thermal initiation followed by curing at elevated temperatures or under radiation.
Thus, there clearly exists a need for unsaturated polyester resin compositions for gelcoats, for lamination purposes and for composites which compositions comprise vinyl ethers and which are curable at room temperature under normal conditions.
An object of the present invention is to provide unsaturated polyester resin compositions which comprise divinyl ethers and which compositions are curable under normal conditions at room temperature. A further object of the present invention is to provide a method for the manufacture of such polyester resin compositions, and a still further object of the invention is the use of said compositions.
The characteristic features of the unsaturated polyester resin compositions comprising divinyl ethers, the method for the manufacture thereof and the use thereof are set forth in the claims.
In accordance with the invention, the unsaturated polyester resin composition comprises at least one unsaturated polyester and at least one divinyl ether, and the curing of the composition may be conveniently performed with radical curing such as peroxide initiator systems under normal curing conditions at room temperature. The curing may be enhanced by using in the formulation a portion of at least one modified polyester such as methacrylate or acrylate modified polyester, and optionally a catalytic amount of a copromoter. Various divinyl ethers or mixtures thereof may be used for partly or totally replacing of monomers, in particular harmful monomers, such as styrene, in unsaturated polyester resin compositions.
The unsaturated polyester resin compositions comprising divinyl ethers are compounded of at least one and preferably two to four unsaturated polyester. Suitable starting materials for the manufacture of normal or modified unsaturated polyesters are listed in the following. As sources of unsaturation, ethylenically unsaturated acids such as maleic acid, fumaric acid, maleic anhydride, derivatives thereof or mixtures thereof are used in an amount of at least 10 mol-%, preferably at least 20 mol-%. As other acids may be used benzoic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, terephtalic anhydride, adipic acid, 1,2-cyclohexyl dicarboxylic acid and 1,4-cyclohexyl dicarboxylic acid. For replacing partially or totally the said ethylenically unsaturated acids, optionally methacrylic acid or acrylic acid may be used in an amount of not more than 40 mol-% and preferably not more than 30 mol-% calculated from the amount of all components, for raising the degree of unsaturation and the reactivity of the polyester resin.
Suitable alcohols required as other components in the unsaturated polyester are monoalcohols, diols, triols, aliphatic alcohols and aromatic alcohols. Preferred saturated aliphatic diols and triols have a general formula (I) 
wherein
X is C1-C4, (CH2xe2x80x94CH2xe2x80x94O)n or 
xe2x80x83and n=1,2,3;
R is H, xe2x80x94CH2OH, xe2x80x94CH3, xe2x80x94CH2CH3, xe2x80x94CH2CH2CH3 or xe2x80x94CH2CH2CH2CH3 and
Rxe2x80x2 is H, xe2x80x94CH2OH, xe2x80x94CH3, xe2x80x94CH2CH3, xe2x80x94CH2CH2CH3 or xe2x80x94CH2CH2CH2CH3.
Particularly preferred alcohols are 2-ethyl hexanol, benzyl alcohol, 2-phenylethyl alcohol, ethylene glycol, diethylene glycol, dipropylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butane diol, 2-methyl-1,3-propane diol, neopentyl glycol, 2-butyl-2-ethyl-1,3-propane diol, 1,6-hexane diol, trimethylol propane and tri-methylol ethane.
The alcohols may also be partly replaced by glycidyl compounds in order to obtain low molecular weight methacrylate or acrylate modified or terminated polyesters. Suitable glycidyl compounds are glycidyl methacrylate and glycidyl acrylate. At most 80 mol-% of alcohols can be replaced by glycidyl compounds and preferably not more than 60 mol-%.
The ratio of acids to alcohols generally used in polyesters of the state of the art may be applied.
The resins are processed in conventional reactors for polyesters until an acid value of 5-65 is reached and excess water is removed during the reaction. During the addition of endcappers, if any, which here refer to glycidyl compounds, the reaction temperature may be decreased, if necessary.
The unsaturated polyester resin composition in accordance with the invention containing divinyl ether comprises:
50-90 wt-%, preferably 58-80 wt-% of at least one, preferably two to four normal unsaturated polyester and/or modified unsaturated polyester;
not more than 30 wt-%, preferably not more than 20 wt-% of styrene;
not more than 20 wt-%, preferably not more than 15 wt-% of at least one monofunctional and/or one multifunctional monomer, such as a derivative of acrylic or methacrylic acid, such as methyl methacrylate, butyl acrylate, ethylhexyl acrylate, hydroxypropyl methacrylate, lauryl acrylate, stearyl methacrylate, lauryl methacrylate, butanediol diacrylate, ethyleneglycol dimethacrylate, diethyleneglycol dimethacrylate, triethyleneglycol dimethacrylate, propyleneglycol dimethacrylate, dipropyleneglycol dimethacrylate, tripropyleneglycol dimethacrylate or trimethylol propane triacrylate, pentaerythritol 3-acrylate, pentaerythritol tetra-acrylate or a vinylic derivative such as divinyl benzene, xcex1-methyl styrene, o-methyl styrene or p-methyl styrene;
0.1-40 wt-%, preferably 5-40 wt-% of at least one divinyl ether, preferably tri-ethylene glycol divinyl ether, diethylene glycol divinyl ether, 1,4-cyclohexane dimethylol divinyl ether, dipropylene glycol divinyl ether, tripropylene glycol divinyl ether, 1,6-hexanediol divinyl ether or 1,4-butanediol divinyl ether; and
optionally additives, such as promoters.
The unsaturated resin compositions in accordance with the invention can be used as such and they are curable at room temperatures by suitable promoter-catalyst systems known in the art.
The obtained resin compositions are well suited for applications where good mechanical properties are required. They show a remarkable benefit in solubility, in applicability and in the properties of the finished cured products. They may be used as such or together with reinforcing agents, filled or unfilled to produce composites, moulds, moulded parts, laminates of 2-20 mm thickness and coatings with a thickness of 200-2000 xcexcm, typically 400-1000 xcexcm for various conventional applications. The resin compositions in accordance with the invention may also be formulated together with suitable additives known in the art to form gelcoats, laminates and polyester products. Surprisingly even thick coatings, products and gelcoats comprising the composition according to the invention can be conveniently cured at room temperature using conventional radical curing. Additionally, in the compositions according to the invention, the molar ratio of divinyl ethers with respect to starting materials in the polyesters can be varied because of high degree of crosslinking.
Gelcoats are curable compositions, which comprise at least one of the above polyester resin compositions and additives. Suitable additives include pigments, fillers, promoters, co-promoters, thixotropic agents, thixotropy enhancers, suppressants, air release agents, surface tension agents, wetting agents, levelling agents and catalysts.
Preferably, the following additives are used for gelcoats according to the invention;
0.1-0.5 wt-% of a metal promoter, preferably such cobalt, manganese, iron, vanadium, copper or aluminium salt of an organic acid, such as octanoic acid or naphthoic acid;
0.1-0.5 wt-% of an amine promoter, such as dimethylaniline, diethylaniline, 2-aminopyridine, N,N-dimethyl acetoacetamide, acetoacetanilide or other organic compounds, such as ethyl acetoacetate, methyl acetoacetate, N,N-dimethyl-p-toluidine, or N,N-dimethyl-o-toluidine;
not more than 10 wt-%, preferably not more than 6 wt-%, of a copromoter, preferably acetoacetoxy ethyl methacrylate or acrylate or C1-C8 linear or branched alkyl acetoacetate; and
0.5-3 wt-% of a peroxide catalyst to initiate the polymerization of the composition, preferably methyl ethyl ketone peroxide or benzoyl peroxide.
A typical gelcoat composition based on the unsaturated polyester resin composition in accordance with the invention comprises:
10-90% Unsaturated polyester resin composition
1-20% Pigments
1-40% Fillers
0-10% Silica
0.5-3% Peroxide type catalyst for initiating the polymerisation of the composition
0.1-5% Promoters.